Pulse communication system



Aug. 12, 1947. J'. B. ATwooD ETAL PULSE COMMUNICATION SYSTEM Filed Feb.17, 1944 2 Sheets-Sheet l .Hip

llg. l2, 1947. J. B. ATwooD ETAL PULSE COMMUNICATION SYSTEM FiledFebQl?, 1944 2 sheets-sheet 2 M S Ria Y Of E TNW m mfg@ mi?? MM) PHY aa,

Patented Aug. 12, 1947 UNITE STTES PULSE COMMUNICATION SYSTEMApplication February 17, 1944, Serial No. 522,758

30 Claims. (Cl. Z50- 15) This invention relates generally to a radiorelaying system, and more particularly to such a system employing pulsesof high frequency energy which are short compared to the time intervalsbetween them for transmitting the radio signals.

An object of the present invention is to enable the eicient receptionand retransmission of modulated pulses of high frequency energy in aradio relaying system.

Another object is to provide a repeater station for use in a radio relaysystem, which receives and retransmits pulses of high frequency energyand which overcomes the eects of extraneous feed back between receivingand transmitting antennas.

A further object is to provide a repeater station for use in a pulsecommunication radio relay system which introduces a delay between thereceived and retransmitted pulses and utilizes the received pulses toblock the receiving channel in the intervals between received pulsesduring which intervals the delayed pulses are retransmitted.

A still further object is to provide a system for generating pulses andfor modulating the width of the generated pulses in accordance withsignal modulation,

A still further object is to provide a system for converting widthmodulated pulses to phase modulated pulses.

The following is a more detailed description of the inventionaccompanied by a drawing, wherein:

Fig. 1 illustrates a preferred form of repeater station in accordancewith the invention for use in a pulse communication radio relay system,and

Fig. 2 is av circuit diagram of the coupling tubes, delay networks andreceiver channel blocking device of Fig. 1.

Referring to Fig. 1, there is shown a repeater station which isillustrative of any one or more similar intermediate stations locatedbetween terminal transmitter and receiver stations of a radio relayingsystem for carrying on communication by means of pulses of highfrequency energy. The terminal transmitter station is not shown since itmay comprise any known type of station for radiating relatively shortduration pulses of carrier frequency. The pulse rate or phasing of thesepulses may be modulated in accordance with the signal modulations. Theterminal receiver station which is also not shown may comprise any knowntype of station for receiving these modulated pulses. By way of eX-ample only, and not by way of limitation, reference may be had toPeterson copending application Serial No. 431,617, filed February 20,1942, for details of one type of pulse transmitter and receiver whichcan be employed at the `terminals, and to Dow copending applicationSerial No. 482,578, led April 10, 1943, for another type of transmitterwhich can be employed as a transmitting terminal.

Broadly stated, the repeater or relay station of Fig. 1 comprisesreceiving and transmitting antennas, labeled as such, and circuits fordelaying the received pulses prior to reradiating similar pulsescontaining the signal modulation. A blocking device is employed forrendering the receiver channel of the repeater station insensitiveduring the periodbetween incoming pulses,

i and the delayed pulses are retransmitted during the time the channelis insensitive. In this Way it is impossible for the retransmittedpulses to be fed back over the ether to the receiving antenna and thenthrough the circuits in the output of the receiver to produce undesiredsinging. By modulating the amount of delay of the pulses at the repeaterstation, it is possible for the attendant at the repeater station tobreak in on the circuit and send a, message along the chain of stationstoward the terminal receiver. Circuits are provided, as will appearhereinafter, for removing noise from the incoming signals. There is alsoprovided a local monitor at the repeater station for enabling theattendant to listen to the incoming signals. A pulse selective circuitfollowed by a limiter serves to eliminate undesired interference in thelocal monitor.

In Fig. 1, the graphical representation of the different outputs fromthe various circuit stages is given immediately above the connections inwhich these outputs appear, in order to aid in an understanding of thefollowing description.

Let us assume that the pulses of high frequency energy originating atthe terminal transmitter have an average pulse rate (unmodulatedcondition) of twenty kilocycles and that the vpulse repetition rate orpulse frequency is modulated in accordance with the signals to betransmitted in a range between plus three kilocycles and minus threekilocycles. The modulation may be either speech or keyed tone, .and thehighest modulation frequency should be considerably lower than the pulserepetition rate. The pulses will then Vary in rate between seventeenkilocycles and twentythree kilocycles and will be received on thereceiving antenna and amplified in radio frequency amplifier 90. Afrequency converter 9| having in circuit therewith a local heterodyneoscillator 93 will change the carrier frequency of the incoming pulsesto a lower or intermediate frequency which is amplified in 92. The intermediate frequency amplifier 92 preferably comprises several stages ofscreen grid tubes. The pulses of intermediate frequency energy are thenrectified by rectifier 94 whose output contains noise ripples. Therectied pulses then are applied to a clipper 95 which removes a portionof the rectified pulse between the top and bottom to thereby provide aclean pulse having the noise ripples removed. In other words, theclipper is a top and bottom limiter which removes noise and variationsabove and below certain limits. In practice, the clipper may consist ofa Ypair of threshold devices in cascade and whose grid biases are sovadjusted that it is possible to utilize any desired portion between thetop and bottom of the incoming pulses. The clipped pulses are invertedrelative to the rectified output from 94 (i. e., in a negativedirection), and these negative pulses then impressed upon a couplingtube structure which has two outputs, one of which goes to the pulserate rselective circuit |0| of the local monitor .circuit and the otherof which goes to another coupling tube structure |02. The output pulsesfrom |00 which are applied to apparatus |02 are of positive polarity.

Coupling tube stages |00 and |02 each include a pair of electrodestructures, aswill appear in more detail from a description of Fig. 2.

Coupling tube stage |02 has two outputs, one being applied to anadjustable delay circuit |93 for controlling the timing of theretransmitted pulse, and the other to an independently adjustable delaycircuit |04. The outputs from |02, it should be noted, are invertedrelative to the -positive character of the pulses applied to the inputof this'same stage. Delay circuit |03 includes a diiferentiator forproducing sharp peaked impulses from the slopes ,or wave fronts of theapplied pulses and also an arrangement for enabling only the positivepeak to pass therethrough having a desired time delay. This positivepeak is Obtained from the trailing edge of the negative output pulsefrom a trigger circuit.

The positive peak impulse from delay circuit |03 serves to control apulse generator |05 which is normally inactive and responds to thepositive peak impulse to produce a pulse which is delayed relative tothe corresponding pulse received on the receiving antenna. Putting it inother words, pulse generator |05 is a circuit which requires a trippingpulse to render it active and whose time constants are such that itrestores itself to the stable state a short time after it has beentripped. Several such pulse generators are known in the art. One type isgenerally referred to as an electronic trigger circuit having one degreeof electrical stability. Such a trigger may comprise two evacuatedelectron discharge devices whose grids and anodes are coupled together`in regenerative manner. Another type is the blocking oscillator normallybiased to the anode current cut-off condition. The output from pulsegenerator |05 comprises a series of pulses corresponding to the seriesof pulses received on the receiving antenna but delayed by a desiredtime interval, and these delayed pulses, after amplification inmulti-stage power amplifier |06, serve to control the generation of highfrequency pulses from a pulse rcontrolled generator |01. The output ofgenerator |01 is radiated from transmitting antenna. The

high frequency generator may be any suitable type, such for example as amagnetron, or the kind shown in Peterson copending application SerialNo. 431,617, supra.

From the foregoing, it will be appreciated that delay network |03affords a possibility of adjustment or modulation of the amount of delayof the outgoing signal pulses limited to an interval between incomingpulses. For enabling the attendant at the repeater station to break inand transmit messages, there is provided a local modulation circuit,either speech or keyed tone, which is impressed on audio amplifier |08,in turn controlling the amount of delay of delay network |03. Therepeater station attendant can thus superimpose his own message (as avariable pulse rate) on the repeated signals whenever it is desired tocommunicate between the repeater station and any one or more subsequentstations in the direction of the receiving terminal.

The output from adjustable delay circuit Hit is a series of pulses ofnegative direction, and these pulses control blocking device |09 toblock the receiving channel at the intermediate frequency amplifierstages 92 during the interval between received pulses, The delay circuit|04 assures the fact that the incoming pulses are passed by thereceiving channel (through the intermediate frequency amplifier stage)without cutting off parts of the received pulses, before the blockingdevice |09 functions to block the receiving channel. Otherwise, that is,in the absence of delay |04, the receiver channel might be blocked offbefore the end of a pulse is completely received. Blocking device |09assures the fact that the receiver is insensitive for a desired intervalbetween received pulses. In the preferred form of the invention, theblocking device functions to reduce the voltage on the screen gridelectrodes of the intermediate frequency amplifiers 92, as will appearlater from the description of Fig. 2. It should be noted that the outputpulses from blocking device |09 are in a negative direction.

The delay circuit |03 is so adjusted that the signals are retransmittedover the transmitting antenna during the interval between receivedpulses, at which time the receiving channel is blocked off. Otherwise,the retransmitted pulse might be picked up by the receiving antenna andcause singing or undesired feed back.

The local monitor circuit comprises a pulse rate selective circuit |0|which reshapes or converts the pulses applied thereto by coupling tubestructure |00 to a substantially sine wave form. In practice, theselective circuit itil may comprise two coupled parallel tuned circuitseach properly damped so that the overall circuit gives a :dat top oruniform response over the range from seventeen kilocycles totwenty-three kilocycles. Although the output from pulse rate selectivecircuit |94 is of sine wave form, modulated between seventeen kilocyclesand twenty-three kilocycles, there are also present slight amplitudevariations which are removed by limiter H9. Limiter |0 preferablycomprises two screen grid vacuum tubes in cascade. The screen grids ofthese limiters are supplied with a low positive polarizing potential toassure a flat anode current output. The output from the limiter H0 is asine wave modulated between seventeen kilocycles and twenty-threekilocycles and is applied to a balanced discriminator and detectorcircuit which converts the pulse yrate or frequency modulation toamplitude modulation. The audio modulation from the rectiers coupled tothe output of the discriminator is then passed on to a low pass lter 2which removes the components above three kilocycles. This filtered audiomodulation is then amplied in audio amplier ||3 and heard in acoustictransducer H4 or recorded in any other suitable utilization device.

Fig. 2 shows the detailed circuits of the coupling tube structures 00,|02y the delay networks |03, and the blocking device v| 09. The sameparts of Figs. 1 and 2 are labeled with the same reference numerals. Thecoupling tubes and |02 each comprise a pair of separate three-electrodestructures Within a single evacuated envelope.

In the operation of the circuits of Fig. 2, the application of anegative pulse -from the output of clipper S to lead I0 will produce apositive pulse in the anode circuit of one of the electrode structuresof coupling tube |00. This positive pulse is applied in parallel to thetwo grids of coupling tube |02 via lead and also applied to the grid ofthe other electrode structure of coupling tube |00 through condenser |2.The pulse applied to the lower electrode structure of coupling tube |00is inverted in its anode circuit and appears as a negative pulse whichis then passed on to the pulse rate selective circuit |0 The anode ofone electrode structure of coupling tube |02 supplies a negative pulseto the trigegr circuit I3 of the delay network |03, while the otheranode of tube |02 supplies a negative pulse to the delay network |04.Delay circuit I|04 is shown only in box form lbecause it is identicalwith delay circuit |03 except for the fact that a negative pulse istaken from the coupling tube of |04 to operate the blocking device |09,lwhereas a positive pulse is taken from the coupling tube of the delaycircuit |03.

Delay network |04 includes a trigger circuit like trigger circuit |3 ofdelay circuit |03. This trigger circuit comprises a pair of evacuatedtriode structures having their grids and anodes interconnectedregeneratively. These trigger circuits have one degree of electricalstability, and require a tripping pulse to change the trigger from thestable to the active state. The trigger, when tripped, will remain inthe active state for a time interval depending upon its time cnstants,after which it restores itself to normal. The trigger is so arrangedthat when one electrode structure thereof passes current, the other willbe non-conductive, and vice-versa. Although the electrode structures ofthe trigger circuits have been shown contained Within a single envelope,it will be evident that the tube structures can have individualenvelopes, if desired.

Considering the delay network |03 for the present, the application of anegative tripping pulse from coupling tube |02 to the grid of thenormally conducting electrode'structure of trigger |3 will trip thetrigger to its active state. A negative output pulse is taken fromtrigger I3 and supplied to lead is. This output pulse is differentiatedby condenser |5 and resistor I6 and the positive peak impulse resultingfrom this differentiation is utilized to render vacuum tube I1conducting. The diiferentiator circuit l5, I6 serves to convert thestart and trailing edges of the rectangular pulse in the output oftrigger |3 to sharp triangular pulses of opposite polarities. Vacuumtube I7 is normally biased to cut-off and requires a positive pulse toovercome its negative grid bias and thus render the tube conducting. Theoutput from tube |'l is a sharp positrigger |3 depends upon the timeconstants of the circuit and upon the value or" the bias on the grid G.The bias on grid G is in turn dependent upon the adjustment of theresistor 20. Since it is only the trailing edge of this output pulsewhich produces the sharp positive triangular-shaped peak impulse in thedifferentiator, in turn controlling the transmitter, it will beappreciated that the circuit |03 delays the transmission of signalpulses by the length or duration of the trigger output pulse, and byvarying this duration it is possible to vary the timing of thegeneration of currents by the transmitter. In order to enable the localattendant to superimpose a variable pulse rate on the retransmittedsignals, whenever he desires to break in on the circuit, the resistor 20is connected in series with the secondary winding of an audiotransformer 2|, the latter in turn being connected to audio amplier |08.Circuit |08 is connected to a suitable local modulation device, such asa microphone, as shown. The result of this local modulation circuit isto produce phase modulated pulses.

Considering now the action of delay circuit I0@ and device |09, anegative output pulse from coupling tube |02 applied to the grid of thenormally conducting electrode structure of the trigger of circuit |04will trip this trigger to its active state. A negative output pulse istakenv from the plate of the coupling tube of delay circuit |04 and issupplied to the blocking oi device |09. Device |99 includes a trigger|20 having one degree of electrical stability and a Vacuum tubeV |2| inits output circuit, in turn coupled to the screen grids of theintermediate frequency ampliers 92. The negative pulse from delaycircuit |04 is applied to the normally conducting electrode structure oftrigger 20 in order to trip this trigger. Vacuum tube 2| is normallybiased to cut-ofland requires a positive pulse on its grid to overcometheV cut-on" bias and thus render the tube conducting. The anode of tube|2| obtains its positive .polarizing potential through a voltage dividercomposed of resistors 22 and 23 connected to a source of 250 voltspositive. A large condenser 25 in shunt to resistor 23 minimizesfluctuations in voltage across this resistor. The anode of tube |2| isalso directly connected to the screen grid electrodes of theintermediate frequency ampliiiers 92. It will thus be seen that thescreen grids of intermedin ate frequency ampliiiers 92 and the anode oftube |2| obtain their positive polarizing potentials from the sameconnection through a resistor 2li. The application of a positive pulseto the control grid of tube |2|, obtained from trigger |20, will causetube |2| to pass current, as a result of which current flows inresistors 22 and 24 and produces an IR drop which reduces the screengrid voltage available for the amplifiers. This reduction in thescreengrid voltage for the intermediate frequency ampliers 92 rendersthese ampliiiers insensitive and cuts off the receiving channel. Theadjustment of cathode resistor |22 in trigger circuit |20 provides avariation in the amount of time that the receiver channel is blocked.The delay circuit IM is so designed that its inherent delay delays theoperation of circuit |09 with respect to the negative tripping pulseapplied to |04.

It will be evident from the foregoing that incoming signal pulses ofvariable pulse rate or phase which are collected on the receivingantenna will modulate or control the transmitter at the repeater stationto cause it to send out pulses of similar variable pulse rate or phase.Also, that the incoming pulses are so spaced and the time constants ofthe repeater station so arranged that the receiving channel is blockedoff' between incoming pulses, at which time the local transmitter isturned on.

What is claimed is:

1. A relay station for relaying pulses of high frequency energy whichhave a short duration relative to the time interval between themcomprising a receiving antenna, a receiver coupled to said antenna andhaving means for changing said pulses of high frequency energy to pulsesof direct current, a clipper coupled to the outut of said receiver forremoving noise ripples in said direct current pulses, a coupling tubecoupled to said clipper and providing two outputs. separate pulse delaycircuits for said last two outputs, a blocking device coupled betweenone of said delay circuits and said receiver, said blocking device beingso constructed and arranged and said one delay circuit having such timeconstants that said receiver is blocked during the interval betweenincoming pulses of high frequency energy, a pulse generator coupled tosaid other delay circuit and responsive to a pulse therefrom. forproducing another pulse of desired polarity, said other delay circuitproviding such, delay that the pulse produced by said pulse generatoroccurs during the interval between incoming pulses of high frequencyenergy at which time the receiver is blocked, a radio frequencygenerator coupled to said pulse generator and responsive to a pulsetherefrom to produce a pulse of radio frequency energy, and atransmitting antenna coupled to the output of said radio frequencygenerator.

2. A relay station for relaying pulses of high frequency energy whichhave a short duration relative to the time interval between themcomprising a receiving antenna, a receiver coupled to said antenna andhaving means for changing said pulses of high frequency energy to pulsesof direct current, a clipper coupled to the output of said receiver forremoving noise ripples in said direct current pulses, a coupling tubecoupledr to said clipper and providing two outputs, sepa# rate andindependently adjustable pulse delay circuits for said last two outputs,a blocking device coupled between one of said delay circuits and saidreceiver, said blocking device being so constructed and arranged andsaid one delay circuit having such time constants that said receiver isblocked during the interval between incoming pulses of high frequencyenergy, a pulse generator coupled to said other delay circuit andresponsive to a pulse therefrom fo-r producing another pulse of desiredpolarity, said other delay circuit providing such delay that the pulseproduced by said pulse generato-r occurs during the interval betweenincoming pulses of high frequency energy at which time the receiver isblocked, a radio frequency generator coupled to said pulse generator andresponsive to a pulse therefrom to produce a pulse of radio frequencyenergy, and a transmitting antenna coupled to the output of said radiofrequency generator, and a monitor circuit also coupled to the output ofsaid receiver, said monitor including a pulse rate selective circuit, alimiter, a discriminator and an audio frequency utilization circuit.

3. A relay station for relaying pulses of high frequency energy whichhave a short duration relative to the time interval between themcomprising a receiving antenna, a receiver coupled to said antenna andhaving means for changing said pulses of high frequency energy to pulsesof direct current, a clipper coupled to the output of said receiver forremoving noise ripples in said direct current pulses, a coupling tubecoupled to said clipper and providing two outputs, separate pulse delaycircuits for said last two outputs, a blocking device coupled betweenone of said delay circuits and said receiver, said blocking device beingso constructed and arranged and said one delay circuit having such timeconstants that said receiver is blocked during the interval be'- tweenincoming pulses of high frequency energy, a pulse generato-r coupled tosaid other delay circuit and responsive to a pulse therefrom forproducing another pulse of desired polarity, said other delay circuitproviding such delay that the pulse produced by said pulse generatoroccurs during the interval between incoming pulses of high frequencyenergy at which time the receiver is blocked, a local modulation circuitfor controlling the amount of delay provided by said last delay circuit,a radio frequency generator coupled to said pulse generatorV andresponsive to a pulse therefrom to produce a pulse of radio frequencyenergy, and a transmitting antenna coupled to the output of said radiofrequency generator.

4. A relay station for relaying pulses of high frequency energy whichhave a short duration compared to the time intervals between themcomprising a receiver coupled to said antenna and having means forchanging said pulses of high frequency energy to pulses of directcurrent, a top and bottom clipper stage for removing noise from saiddirect current pulses, a pulse rate selective circuit coupled to theoutput of said clipper, a limiter coupled to the output of saidselective circuit, a balanced discriminator and detector coupled. to theoutput of said limiter for changing frequency or phase variations in theoutput of` said limiter to variations in amplitude, a low pass filterfor passing the rectified output of said discriminator, and an audiofrequency utilization circuit coupled to said filter, an adjustabledelay circuit also coupled to the output of said clipper, a pulsegenerator coupled to said delay circuit and responsive to a pulsetherefrom for producing another pulse of desired polarity, a radiofrequency transmitter coupled to said pulse generator and responsive toa pulse therefrom to produce a pulse of radio frequency energy, and atransmitting antenna for said transmitter, said delay circuit providingsuch delay that the pulse producedY thereby occurs during the intervalbetween incoming pulses of high frequency energy applied to saidreceiver.

5. A relay station for relaying pulses of high frequency energy whichhave a short duration compared to the time intervals between themcomprising a receiver coupled to said antenna and having means forchanging said pulses of high frequency energy to pulses of directcurrent, a top and bottom clipper stage for removing noise from saiddirect current pulses, a pulse rate selective circuit coupled to theoutput of said clipper, a limiter coupled to the output of saidselective circuit, a balanced discriminator and detector coupled to theoutput of said limiter for changing frequency or phase variations in theoutput of saidlimiter to variations in amplitude, a low pass 9 filterfor passing the rectied output of said discriminator, and an audiofrequency utilization circuit coupled to said lter, iirst and secondadjustable delay circuits having their inputs coupled in parallel to theoutput of said clipper, a blocking device coupled between said iirstdelay circuit and said receiver, said blocking device being soconstructed and arranged and said first delay circuit having such timeconstants that said receiver is blocked during the interval betweenincoming pulses oi high frequency energy applied to said receiver, apulse generator coupled to said second delay circuit and responsive to apulse therefrom for producing another pulse of,

desired polarity, a radio frequency transmitter coupled to said pulsegenerator and responsive to a pulse therefrom to produce a pulse ofradio frequency energy, and a transmitting antenna for said transmitter,said second delay circuit providing such delay that the pulse producedthereby to control said pulse generator occurs during the intervalbetween pulses of high frequency energy applied to said receiver.

6. A relay station for relaying pulses of high frequency energy whichhave a short duration compared to the time intervals between them, areceiving antenna, a receiver coupled to said antenna and having meansfor rectifying vsaid pulses, a coupling tube responsive to said rectiedpulses for producing two pulse outputs of diierent polarities, a monitorcircuit for one of said outputs, another coupling tube for the otheroutput, said last coupling tube also providing two pulse outputs of thesame polarity, separate pulse delay circuits for said last two pulseoutputs, a blocking device coupled between one of said delay circuitsand said receiver, said blocking device being so constructed andarranged and said one delay circuit having such time constants that saidreceiver is blocked during the interval between incoming pulses of highfrequency energy, a pulse generator coupled to said other delay circuitand responsive to a pulse therefrom for producing another pulse ofdesired polarity, said other delay circuit providing such delay that thepulse produced by said pulse generator occurs during the intervalbetween incoming pulses f high frequency energy at which time thereceiver is blocked, a radio frequency generator coupled to said pulsegenerator and responsive to a pulse therefrom to produce a pulse ofradio frequency energy, and a transmitting antenna coupled to the outputoi said radio frequency generator.

7. A pulse delay circuit comprising a trigger circuit having a pair ofvacuum tube electrode structures, the grids and anodes of said vacuumtube electrode structures being cross-coupled, means for unsymmetricallybiasing the grids to thereby produce a trigger circuit having one degreeof electrical stability, a connection for supplying a unidirectionalcurrent tripping pulse of predetermined polarity and magnitude to saidtrigger circuit for changing it from its stable to its active state, avacuum tube normally biased to cut-off, a diierentiator circuit coupledbetween the negative pulse output terminal of said trigger circuit andthe input of said last vacuum tube, said diiierentiator circuit servingto produce a sharp positive pulse from the trailing edge of the negativeoutput pulse produced by said trigger of such magnitude as to overcomethe cut-off bias of said last tube and render it momentarily conductive,said last tube producing a pulse when it becomes momentarily conductive,and a pulse reaizait l0 sponsive circuit coupled to the cathode of saidlast tube.

8. In combination, a pulse delay circuit comprising a trigger circuithaving a pair of vacuum tube electrode structures, the grids and anodesof said vacuum tube electrode structures being cross-coupled, means forunsymmetrically biasing the grids to thereby produce a trigger circuithaving one degree of electrical stability, a connection for supplying aunidirectional current tripping pulse of predetermined polarity andmagnitude tc said trigger circuit for changing it from its stable to itsactive state, a vacuum tube normally biased to cut-oir, a diiferentiatorcircuit coupled between the negative pulse out- I put terminal of saidtrigger circuit and the input of said last vacuum tube, saiddiiierentiator circuit serving to produce a sharp positive pulse fromthe trailing edge of the negative output pulse produced by said triggerof such magnitude as to overcome the cut-olf bias of said last tube andrender it momentarily conductive, said last tube producing a pulse `whenit becomes momentarily conductive, and a radio transmitter normallybiased to cut-off coupled to an electrode of said last tube andresponsive to the pulse produced thereby to generate a pulse of highfrequency energy.

9. A p-ulse delay circuit comprising a trigger circuit having a pair ofvacuum tube electrode structures, the grids and anodes of said vacuumtube electrode structures being cross-coupled, means for unsymmetricallybiasing the grids to thereby product a trigger circuit having one degreeof electrical stability, a connection for supplying a unidirectionalcurrent tripping pulse of predetermined polarity and magnitude to saidtrigger circuit for changing it from its stable to its active state, avacuum tube normally biased to cut-off, a diierentiatcr circuit coupledbetween the negative pulse output terminal of said trigger circuit andthe input of said last vacuum tube, said diferentiator circuit servingto produce a sharp positive pulse from the trailing edge of the negativeoutput pulse produced by said trigger of such magnitude as to overcomethe cut-off bias of said last tube and render it momentarily conductive,said last tube producing a pulse when it becomes momentarily conductive,and a pulse responsive circuit coupled to an electrode of said tube andresponsive to the pulse produced thereby to generate another pulse ofthe same relative polarity.

10. In combination, an electron discharge device trigger circuit havingone degree of electrical stability, a connection for supplying aunidirectional current tripping pulse of a predetermined polarity andmagnitude to said trigger circuit for changing it from its stable to itsactive state, an electron discharge device normally biased to cut-off, adiierentiator circuit coupled :between the negative pulse outputterminal of said trigger circuit and the input of said last electrondischarge device, said dirferentiator circuit serving to produce a sharppositive pulse from the trailing edge of the negative output pulseproduced by said trigger circuit of such magnitude as to overcome thecut-oir" bias of said device and render it momentarily conductive, saidlast device producing a pulse when it becomes momentarily conductive. Y

11. A phase modulation pulse system comprising a trigger circuit havingone degree' of electrical stability, said trigger having a stable stateand an active state, a source of recurring pulses for repeatedlytripping said trigger at the rate of said recurring pulses, and meansfor varying the active time of said trigger in accordance with signalmodulation to thereby produce output pulses from said trigger circuitwhose width varies in accordance with said modulation, a differentiatorcircuit for producing short pulses from the trailing edges of saidvariable width pulses, and a utilization circuit responsive solely tosaid short pulses produced from said trailing edges.

12. A phase modulation pulse system comprising a trigger circuit havingone degree of electrical stability, said trigger having a stable stateand an active state, a source of recurring pulses for repeatedlytripping said trigger at the rate of said recurring pulses, and meansfor varying the active time of said trigger in accordance with signalmodulation to thereby produce output pulses from said trigger circuitwhose width varies in accordance with said modulation, a differentiatorcircuit for producing short pulses from the starting and trailing edgesof said variable width pulses, means for discarding the short pulsesobtained from said starting edges, and means for utilizing solely thoseshort pulses obtained from said trailing edges.

13. A system in accordance with claim 11, characterized in this thatsaid source f recurring pulses comprises a radio receiver, and saidutilization circuit comprises a radio transmitter.

14. The method of generating phase modulated pulses which comprisesgenerating substantially square wave pulses under control of a series ofrecurring pulses, varying the width of said generated square wave pulsesin accordance with signal modulation, and utilizing the trailing edgesonly of said variable Width pulses to generate additional pulses whosetiming is a function of the signal modulation.

15. In combination, a trigger circuit having one degree of electricalstability and including two electrode structures each comprising ananode, a cathode and a grid, impedance elements interconnecting the gridof each structure with the anode of the other structure in regenerativemanner, a cathode bias resistor for at least one of said structures, asource of tripping pulses for said trigger circuit, and a modulationcircuit coupled to said cathode resistor for varying the bias of saidone structure in accordance with modulation potentials.

16. In combination, a trigger circuit having one degree of electricalstability and including two electrode structures each comprising ananode, a cathode and a grid, impedance elements interconnecting the gridof each structure with the anode of the other structure in regenerativemanner, a common cathode bias resistor for said structures, a source oftripping pulses for said trigger circuit to thereby change said triggercircuit from its stable to its active state, and a signal modulationcircuit coupled to said common cathode bias resistor for varying theactive time of said trigger circuit in accordance with the signalmodulation.

17. A pulse system involving pulses of high frequency energy which havea short duration compared to the time intervals between them, comprisingan antenna, a receiver coupled thereto including a rectifier forrectifying the received pulses, a transmitter under control of saidrectined pulses, and means coupled to said rectier and back coupled to apreceding stage in 'said receiver for blocking said receiver during theintervals between received pulses, said means including an electrondischarge device trigger circuit having an adjustable element forvarying the active time of said trigger circuitto thereby vary the timeof occurrence and the time during which said receiver is blocked.

18. A pulse modulation system comprising a trigger circuit having onedegree of electrical stability, said trigger having a stable state andan active state, a source of recurring pulses for repeatedly trippingsaid trigger at the rate of said recurring pulses, and means for varyingthe active time of said trigger in accordance with signal modulation tothereby produce output pulses from said trigger circuit whose Widthvaries in accordance with said modulation, a differentiator circuit forproducing short pulses from the starting and trailing edges of saidvariable width pulses, and a utilization circuit responsive solely tothose short pulses which are produced from the trailing edges.

19. A receiver for receiving pulses which are modulated in phase ortiming, comprising an electron discharge device stage through which thereceived signal pulses are adapted to pass, and an electron dischargedevice self-restoring trigger circuit responsive to the received signalpulses for blocking the passage of signals through said stage inaccordance with the timing modu lations in the received pulses,

20. A radio receiver adapted to receive pulses which are transmittedfrom a remote radio transmitter and which are modulated in phase ortiming, comprising a receiver having circuits for beating the carrier ofthe incoming signal pulses with locally produced oscillations to therebyproduce pulses of intermediate frequency energy, a screen grid electrondischarge device intermediate frequency amplifier therefor, a rectiercoupled to the output of said amplifier, and vacuum tube circuitsresponsive to the rectied energy for varying the conductivity of saidamplier substantially in accordance with the variations in timing of thereceived pulses, said vacuum tube circuits being coupled between theoutput of said rectifier and the screen grid electrode of said amplier.

2,1. A receiver for receiving pulses which are modulated in phase ortiming, comprising an electron discharge device stage through which thereceived signal pulses are adapted to pass, andra trigger circuitresponsive to the received signal pulses for blocking the passage ofsignals throughY said stage for xed time intervals in accordance withthe timing modulations in the received pulses, said trigger circuitcomprising a pair of vacuuml tube electrode structures Whose grids andanodes are regeneratively coupled together.

22. A receiver for receiving pulses of radio frequency energy which aremodulated in phase or timing comprising an electron discharge devicestage through which the received signal pulses are adapted to pass, adetector circuit following said stage for changing said pulses of radiofrequency energy to unidirectional current pulses, and a trigger circuitcoupled between the output of said detector and said stage for varyingthe conductivity of said stage in accordance with the variations intiming of the received pulses.

23. A pulse system involving pulses of high frequency energy which havea short durationcompared to the time intervals between them, comprisingan antenna, a receiver coupled thereto including a Vrectiiier forrectifying the received pulses, a transmitter under control of saidrectified pulses, and means coupled to said rectii'ler and back coupledto a preceding stage in said receiver for blocking said receiver duringthe intervals between received pulses, said means including an electrondischarge device trigger circuit having an adjustable element forvarying the active time of said trigger circuit to thereby vary the timeof occurrence and the time during which said receiver is blocked.

24. A pulse repeater station comprising pulse receiving apparatus, pulsetransmitting apparatus, a delay circuit between the output of saidreceiver and the input of said transmitter, and means for modulating theeffective amount of delay produced by said delay circuit in accordancewith signal modulation.

25. A radio pulse repeater station comprising radio pulse receivingapparatus, means for converting the received radio pulses tounidirectional current pulses, radio transmitting apparatus, a delaycircuit responsive to said unidirectional current pulses for controllingthe radio transmitting apparatus to send out pulses of energy a desiredinterval of time later than the received pulses, and means formodulating the time delay of said delay circuit in accordance withsignals.

26. A pulse type communication system comprising a pair of stationsseparated by a wave transmitting medium, each station includingapparatus for producing pulses which are short compared to the timeintervals between them, and each station including a receiver fordemodulating received pulses, means associated with each receiver forcontrolling it to be responsive substantially solely at timesregistering with the repetition rate of the incoming pulses, anadjustable pulse delayer in circuit with the receiver of each stationand receiving pulses therefrom, said delayer controlling the rate ofproduction of pulses in the transmitter of the same station, and meanscoupled to said adjustable pulse delayer for modulating the timing ofthe pulses passed thereby to said transmitter.

27. A pulse type communication system comprising a pair of stationsseparated by a wave transmitting medium, each station includingapparatus for producing pulses which are short compared to the timeintervals between them, and each station including a. receiver fordemodulating received pulses, means associated with each receiver forcontrolling it to be responsive substantially solely at timesregistering with the repetition rate of the incoming pulses, an adjust-14 able vacuum tube pulse delayer in circuit with the receiver of eachstation and receiving pulses therefrom, said delayer being soconstructed and arranged as to be responsive to pulses solely of apredetermined polarity above a certain value which are impressed thereonfor controlling the rate of production of pulses in the transmitter ofthe same station, and means coupled to said adjustable pulse delayer formodulating the timing of the pulses passed thereby to said transmitter.

28. A communications system comprising pulse repeater stations, means ateach station to delay and to modulate the delay of pulses transmitted inresponse to received pulses, and demodulating means responsive tomodulations of the frequency of the pulses.

29. A pulse modulation system comprising a trigger circuit having onedegree of electrical stability, said trigger circuit having a stablestate and an active state, said trigger including two electron dischargedevice electrode structures each having an anode, a grid and a cathode,impedance elements cross-connecting the anodes with the grids of thedevices, regeneratively, a direct connection between the cathodes, acommon cathode resistor for said electrode structures, and means incircuit with said common cathode resistor for supplying recurringtripping pulses of a variable pulse rate to thereby cause said triggercircuit to produce unidirectional output pulses containing themodulation components.

30. A communications system comprising pulse repeater stations, means ateach station to delay and to modulate the delay of pulses transmitted inresponse to received pulses, and demodulating means responsive tomodulations of the pulses.

JOHN B. ATWOOD. HAROLD O. PETERSON.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 2,262,838 Deloraine et al Nov.18, 1941 2,266,401 Reeves Dec. 16, 1941 2,113,214 Luck Apr. 5, 19381,433,599 Bown Oct. 31, 1922 2,045,244 Gerhard June 23, 1936 2,199,179Koch Apr. 30, 1940 1,798,066 Clement Mar. 24, 1931 2,034,738 BeverageMar. 24, 1936

